Hemodialysis is a method for removing waste products such as potassium and urea from the blood, such as in the case of renal failure. During hemodialysis, waste products that have accumulated in the blood because of kidney failure are transferred via mass transfer from the blood across a semi permeable dialysis membrane to a balanced salt solution. The efficiency of a hemodialysis procedure depends on the amount of blood brought into contact with the dialysis membrane. A flow of 250 milliliters of blood per minute under a pressure gradient of 100 millimeters of mercury is considered a minimum requirement for adequate dialysis. Over the past several years, flow rates between 350 milliliters per minute and 400 milliliters per minute have become common.
The long hours and the frequency of the dialysis treatment in patients with renal failure require reliable, continued access to the venous system for blood exchange. Long-term venous access mechanisms commonly used for hemodialysis treatment include vascular access ports, dialysis grafts, and hemodialysis catheters. One type of blood treatment catheter that is well-known in the art is a dual or triple-lumen hemodialysis catheter. These catheters are designed to provide long-term access to the venous system for dialysis. The dual-lumen catheter typically has an inflow lumen for withdrawing blood to be treated from a blood vessel and an outflow lumen for returning cleansed blood to the vessel. The distal segment of the catheter is typically positioned at the junction of the superior vena cava and right atrium to obtain a blood flow of sufficient volume to accommodate dialysis treatment requirements. This allows blood to be simultaneously withdrawn from one lumen, to flow into the dialysis circuit, and be returned via the other lumen. Triple lumen catheters function in a similar manner but have an additional smaller lumen which may be used for guidewire insertion, administration and withdrawal of fluids such as drugs or blood sampling, and for injection of contrast media required for imaging procedures.
To optimize blood flow rates during dialysis and reduce treatment times, catheters have been designed to maximize the cross-sectional lumen area of the inflow and outflow lumens. It is well known in the art that blood flow rates are negatively impacted if the cross-sectional area of the lumens does not remain essentially consistent and as large as possible throughout the entire length of the catheter from the proximal portion of the catheter to the distal portion of the catheter. Catheters with large, consistent luminal space typically have exit ports with blunt or flat-faced open tips, so as not to compromise the luminal area. Typically the exit port at the distal end of the catheter is cut at a 90 degree angle to the axis of the catheter.
While blunt, open ended catheters maintain optimal flow rates, they are difficult to insert into the patient because of their blunt leading ends. An introducer sheath will often be used to facilitate insertion. The introducer sheath has a dilating tip which is easily advanced through the track and into the vessel. The sheath has a large lumen into which the blunt-tipped catheter is inserted and advanced into the vessel. Although an introducer sheath may facilitate catheter placement, use of a sheath has several disadvantages. A sheath increases the risk of air embolism due to the presence of air gaps between the sheath and catheter. In addition, procedures that use an introducer sheath result in an enlarged insertion track due to the larger diameter of the sheath relative to the catheter. The use of a sheath also increases procedure time and costs.
A guidewire insertion technique is therefore often the preferred insertion technique for dialysis catheter placement. A guidewire is a thin, flexible wire that is usually made of stainless steel and has an atraumatic tip. A guidewire is typically inserted into a lumen of a dual or triple lumen catheter and then the catheter is advanced over the guidewire through the tissue track and into the vessel. The guidewire also provides additional stiffness or reinforcement in the wall of a catheter, to prevent kinking or accordianing of the catheter shaft as it is advanced through a tissue track and into a vessel.
If a guidewire is used for insertion of a blunt-end catheter with a large distal end opening, excess space will exist between the outer diameter of the guidewire and the inner diameter of the catheter lumen. A close fit between the lumen and the inserted guidewire is not dimensionally possible, thus leaving an annular gap between the guidewire and the distal opening of the catheter lumen. The excess annular space causes the leading distal edge of the catheter to accordion proximally over the guidewire during insertion, resulting in difficulties in advancing the catheter into the vessel. The distal portion of the catheter may grab or snare tissue as the practitioner attempts to advance the catheter into and through the vessel. This can increase procedure time, prevent the practitioner from reaching the intended target site within a patient vessel, or potentially cause other complications.
To overcome insertion difficulties common with inserting blunt tipped catheters, dialysis catheters have been designed with conical tapered distal portions that are narrower compared to the proximal portion of the catheter. The conical tip acts as a dilator to facilitate advancement of the catheter through the tissue track and into the vessel. These conical tip designs may include a guidewire lumen that exits from the distal tip of the catheter through a guidewire opening of reduced diameter, typically 0.037 inches.
While conical, tapered tip designs address the problems associated with inserting blunt tip full lumen distal end designs, they are disadvantageous in that they do not allow for optimum flow rates due to the reduced lumen diameter at the distal tip. To overcome reduced flow rates, conical, tapered tip catheters have been designed with distal side facing port or apertures cut through the catheter sidewall. The ports are located proximal to the conical tapered section and accordingly provide an exit channel from the lumen at a location where the cross-sectional area of the lumen has not been reduced.
Using side holes or apertures eliminates the problems of reduced flow rates but side-facing apertures are more likely to occlude than distally facing apertures. Those side holes located adjacent to the vessel wall are more likely to become blocked by the vessel wall, and are thus prone to clot-formation. In addition, the presence of side holes compromises the effectiveness of a fluid lock. A fluid lock, as known in the art, is used to prevent clot formation within the catheter between dialysis sessions. Typically, a heparin—saline fluid solution is infused into the full length of the catheter lumens. The fluid lock will only be effective up to the first proximal side hole, where the fluid will exit from the catheter and be replaced by blood. In the absence of the heparin-saline fluid solution, a portion of the lumen distal of the first side hole will become occluded by clot formation, complicating future dialysis sessions.
Another common complication of dialysis catheters is occlusion of the inflow and outflow apertures due to contact between the catheter and the vessel wall at the location of the apertures. During dialysis, negative pressure is generated within the inflow lumen in order to draw blood from the vessel through the lumen and into the dialysis machine. The suction created by the negative pressure may cause the catheter to move away from the center of the vessel and into contact with the vessel wall. The vessel wall essentially blocks the aperture, preventing further blood from being drawn into the inflow lumen. Although not as, common, the outflow apertures may also come to rest up against the vessel wall, resulting in occlusion.
Thus, there exists a need in the art for a dual or triple lumen hemodialysis catheter that has a dilating distal tip that is not reduced in lumen cross-sectional area compared to the rest of the lumen. Such a lumen would be able to maintain consistent and optimal blood flow rats throughout the entire length of the catheter, eliminating the need for side hole ports. The catheter would have one lumen capable of receiving a guidewire that can provide enhanced guidewire tracking along various lengths of the catheter, thereby eliminating the need for an introducer sheath. The catheter would be designed to prevent occlusion of the blood lumen apertures by having a distal end shape that creates a barrier between the blood lumens and vessel wall.
A vascular access catheter has not yet been proposed that solves all of the above-mentioned problems. The vascular access catheter described herein addresses problems with prior art catheters by providing a hemodialysis catheter that has at least two lumens, each with at least one aperture, and a distal portion that has one lumen with a substantially open sloped face distal end portion with a distal tip and consistent cross-sectional area compared to the rest of the lumen of the catheter, which allows for maximum blood flow. The catheter also has a third lumen located adjacent the distal tip that is capable of receiving a guidewire. The guidewire aperture and the sloped face of the distal end portion facilitate insertion, without the use of an introducer sheath. The luminal cross-section area is maintained for the entire length of the catheter, eliminating the need for side holes, and thereby avoiding problems associated with compromised fluid lock and resulting side hole occlusion. The catheter may optionally include a curved or bent distal end shape to prevent contact between the lumen apertures and the vessel wall.
Accordingly, provided herein, in one aspect, is a hemodialysis catheter that may have two or three lumens and a sloped open-faced distal end portion that provides for optimal blood flow rats by maintaining a uniform cross-sectional area throughout the lumen, eliminating the need for attachments or additional steps, thereby minimizing procedure time and improving patient treatment outcomes.
A further purpose is to provide a catheter that maintains the cross-sectional area of the blood lumen of the catheter without increasing the outer diameter of the catheter.
A further purpose is to provide a transitional guidewire lumen that is positioned at the distal most edge of the sloped distal end portion of the catheter that does not cause the overall outer diameter of the catheter to be increased.
A further purpose is to provide a catheter that is capable of receiving a guidewire in a third lumen that is designed for optimal guidewire tracking without requiring the use of an introducer sheath. The lumen may extend a partial length of the catheter, where it may be joined to another lumen, or it may extend substantially all the way through to the proximal end of the catheter, which may be useful for injections or infusion of drug treatments.
A further purpose is to provide a catheter that minimizes occlusion of the lumen apertures of the catheter by providing a substantially curved distal portion that abuts against the vessel wall while the catheter is deployed in a vessel. The abutting curved distal portion acts to guard one of the lumen apertures of the catheter from being occluded, which in turn, maintains maximum blood flow.
A further purpose is to provide a catheter that has a distal portion that allows for increased ease of insertion of the catheter into a vessel. The insertion is facilitated by straightening the distal portion of the catheter from a substantially curved to a straight configuration, which causes less resistance upon insertion. The distal portion of the catheter is more flexible, compared to the rest of the catheter, which helps to facilitate straightening of the distal portion. The flexibility of the distal portion of the catheter allows the distal portion to return to its original configuration after the guidewire is removed.
It is a further purpose to provide a catheter that maximizes flow rates without requiring side hole ports.
It is yet another purpose to provide a non-conical distal end portion catheter that may be placed without the use of an introducer sheath.
Various other objectives and advantages will become apparent to those skilled in the art as more detailed description is set forth below. Without limiting the scope of the invention, a summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments may be found in the Detailed Description.